Coversions using math class

Question

public class MeasurementConverterV2_Key
//Purpose of program
    public static void printPurpose( )  //notice that this method is void, nothing is returned
        System.out.println("This program converts to and from");
        System.out.println("English and metric units of measure.");
        System.out.println("=====================================");
    //convert feet to miles
    //the ft parameter receives the value of the feet argument passed from main method.
    public static double convertFeetToMiles(double ft)
        return ft / 5280;     
    //convert miles to feet
    public static double convertMilesToFeet(double mi)
        return mi * 5280;     
    //convert miles to kilometers
    public static double convertMilesToKilometers(double mi)
      return mi * 1.61;      
    //convert kilometers to miles
    public static double convertKilometersToMiles(double km)
        return km / 1.61;    
    //convert pounds to kilograms
    public static double convertPoundsToKilograms(double lbs)
        return lbs / 2.2;  
    //convert kilograms to pounds
    public static double convertKilogramsToPounds(double kl)
        return kl * 2.2;   
    //convert gallons to liters
    public static double convertGallonsToLiters(double gl)
       return gl * 3.79;    
    //convert liters to gallons
    public static double convertLitersToGallons(double lt)
        return lt / 3.79;     
    public static void main(String[ ] args)
        //local variables
        //double miles, feet, inches, pounds, gallons;
       // double kilometers, kilograms, liters;
        //variable declaration and initialization
        printPurpose();                                    //invoke the printPurpose() method
        double feet = 6230;
        double miles = convertFeetToMiles(feet);            //invoke the convertFeetToMiles() static method and pass the feet variable as an argument
        System.out.printf("%8.1f ft. = %7.1f mi. %n", feet, miles);
        miles = 1.9;
        feet = convertMilesToFeet(miles);
        System.out.printf("%8.1f mi. = %7.1f ft. %n", miles, feet);
        miles = 22.3;
        double kilometers = convertMilesToKilometers(miles);
        System.out.printf("%8.1f mi. = %7.1f km. %n", miles, kilometers);
        kilometers = 1000.0;
        miles = convertKilometersToMiles(kilometers);//call method to convert kilometers to miles goes here
        System.out.printf("%8.lf km. = %7.lf mi. %n", kilometers, miles);//print results goes here
        double pounds = 204;
        double kilograms = convertPoundsToKilograms(pounds); //call method to convert pounds to kilograms goes here
        System.out.printf("%8.lf lbs. = %7.lf kl. %n", pounds, kilograms);//print results goes here
        kilograms = 98;
        pounds = convertKilogramsToPounds(kilograms);//declare and initialize the kilograms variable goes here
        System.out.printf("%8.lf kl. = %7.lf lbs. %n", kilograms, pounds);//call method to convert kilograms to pounds goes here
        //print results goes here
        double gallons = 55;//declare and initialize the gallons variable goes here
        double liters = convertGallonsToLiters(gallons);
        System.out.printf("%8.lf gl. = %7.lf lt. %n", gallons, liters);//call method to convert gallons to liters goes here
        //print results goes here
        liters = 2;//declare and initialize the liters variable goes here
        gallons = convertLitersToGallons(liters);//call method to convert liters to gallons goes here
        System.out.printf("%8.lf lt. = %7.lf gl. %n", liters, gallons);//print results goes here
    }//end of main method
}//end of classthis program, when ran, tells me that "UnknownFormatConversionException" and " null(java.util.Formatter). I followed the directions very carefully and made sure everything was spelled correctly; why won't it run passed the point of "kilometers to miles"??

Answer 1

Whenever you get an exception you should do two things:
1.) Look at the stack trace and find the position highest on the stack trace that is your code (i.e. not a class that you didn't write) and look into that line and try to find out what you might be doing wrong there (or just before that)
2.) Look at the API documentation of the Exception class and find out when it's thrown (in this case: look at http://java.sun.com/javase/6/docs/api/java/util/UnknownFormatConversionException.html )
If you still can't figure out the problem post the line where the problem occured.